Regardless of the thermostat setting, the heater becomes too hot to touch on an overnight charge.
Having taken the cover off, there is no apparent damage to the thermostat. However, apart from the obvious fact that it's a bimetal strip, it is not obvious haw it works, as there is very little movement when turning the control from zero to max.
Also, the reset button has a contact similar to car points. How does this work?

Mike, March 2011